Mzt1¹¹/Mzt1⁵⁷ transheterozygous are viable and show apparently normal coordination but males show a progressive decrease in fertility from near normal at eclosion to sterility at 4 weeks after eclosion; this correlates with a progressive decrease in sperm motility i.e. 3-weeks old males produce motile sperm and 5-weeks old males produce non-motile sperm. Females are viable and fertile. In these mutant males, basal bodies are frequently mispositioned in onion-stage spermatids and (more severely) elongating spermatids, the nuclei in bundled spermatid and in late stage spermatid are scattered (instead of being positioned at the bundle tip as in controls), and the sperm tails show misshapen/severely elongated mitochondrial derivatives, but the primary spermatocyte cysts contain the expected 16 cells, the centrosomes organize robust microtubule asters during meiosis, the onion-stage spermatids do not show significant nucleus volume changes, the axonemes in the sperm tail do not show obvious structural defects and the average number of microtubules running along the sperm tail is comparable to controls.